The nets collect a lot of debris and algae so my guess is that they are feeding. It would be nice to ID them and then figure out where they came from since they seem to reproduce and stay in a population without the extreme separating that seems to be necessary with the ones we purchase. I would suggest not mixing them with the ones from Paul just in case the new ones cannibalize the ones that are free growing. You might throw a hand full of the volunteer variety in with the new ones just to see what happens (assuming you could identify which was which).